The present invention relates generally to mechanical linking systems for electronic assemblies and more particularly to removable mechanical attachment systems for butt joined electronic assemblies and modules operating at millimeter wavelength frequencies.
Recent advancements in optical communications technology have demonstrated optical data demuxing at a speed of over 160 Gbit/sec through a single mode optical fiber. At the same time, there is a lack of corresponding progress in test and measurement instrumentation to support analyzing these fast optical pulses. Current solutions are limited by interconnect issues that limit bandwidth and signal integrity, and manufacturing issues that can substantially increase the cost of components. One commercial solution is to couple an enclosed photodetector module with a conventional enclosed sampling head using a coaxial transmission line. The coupled modules are mounted in an optical plug-in module for a sampling oscilloscope. Another solution is to buy a high-speed photodetector as the optical-to-electrical (O/E) converter and use a sampling oscilloscope to capture the signal. This approach seems more beneficial for users because, in addition to having to spend less money, they can also maintain the electrical input to the scope for other testing needs. The inconvenience to users is that the screen is no longer calibrated for accurate power measurements. However, this inconvenience can be overcome by purchasing a separate power meter and perform a calibration manually. Users are faced with the choice of spending more money for the added power level calibration feature of an optical plug-in module or save $10 to 15 thousand dollars by buying a photodetector separately such that both electrical inputs and optical inputs can be measured with the same investment. The latter choice also provides users with a power meter which can be used elsewhere as well.
A common weakness for the above two solutions is that they both need electrical interconnections to connect the photodetector output to the sampler input. Because of the high frequencies involved, the connectors are quite expensive. Moreover, aside from introducing additional costs to the system, these components also introduce unwanted impedance mismatching that produce signal reflections. These signal reflections result in waveform distortion as a function of bit pattern when measuring fast repetitive signals, such as the RZ 40 Gb/Sec optical data.
A solution to these problems is to combine the detector and sampler semiconductor devices together to form a fully integrated photodetector-sampler IC design. This would eliminate all of the interconnecting hardware between the photodiode and sampler. While a fully integrated photodetector-sampler design (FIPS) sounds good, it runs into practical problems during implementation. Generally, test equipment manufactures are not vertically integrated companies that have the processing technology or the equipment to produce FIPS designs. In addition, high speed photodetector manufacturers generally specialize in producing optical components, such as O/E and E/O converters, but not electrical components, such as electrical samplers. Conversely, electrical component manufactures do not manufacture optical components. To produce the FIPS design would require capital investment and technology development by optical or electrical component manufactures or the test and measurement equipment manufacturer.
Another issue with the FIPS design is yield loss of the final assembly if either of the optical detector or sampler sections develop problems. The photodiode performance cannot be accurately characterized until permanently mounted on or within a carrier or housing, an optical fiber aligned to the photodiode, and electrically coupled to the sampler section. If the output of the competed FIPS device does not meet design specifications, it is difficult to determine if the problem has to do with the fiber alignment, photonic and impulse responses of the diode, polarization sensitivity and the like in the optical detector section or signal gain, sensitivity and the like in the sampler section. Even if the performance problem can be identified to one of the sections, replacing the defective section may lead to damage of the other section.
Another problem with the FIPS design is negotiating refunds on defective parts. Since different manufacturers make the components for the optical and sampler sections and one or the other or a system integrator, such as the test and measurement manufacturer, performs the final integration, determining the cause of the failed part or parts in the sections can be a source of conflict. For example, the problem may be determined within the photodetector module, say a lower than spec photo response. The problem could have been caused by the photodiode die being damaged during the FIPS processing; the optical fiber being misaligned from the integrator assembly process; the optical fiber end surface polishing being flawed; the fiber/detector IC junction having foreign contaminations not readily visible to the eye; the wire bond from the detector IC to the sampler IC having excessive inductance introduced by improper wirebonding; the wirebonder damaging the detector IC by improper bonding control, such as excess bond head ultrasonic energy or pressure, and the like. The photodetector IC manufacturer may be reluctant to refund the cost of the multi-thousand dollars detector IC where the defect is caused by a defective assembly process.
What is needed is an electronic assembly and module design that overcomes the shortcomings of the FIPS and the coaxial interconnect designs. The electronic assembly and module design should allow independent testing and verification of separate sections of the assembly prior to final assembly or integration. The electronic assembly or module should allow for easy assembly and alignment of the separate device sections down to the micron level. Further, there is needed for a removable mechanical securing system for joining the separate sections together as a single assembly or module that allows easy disassembly of the joined sections.
Accordingly, the present invention is to a removable mechanical attachment system for joining at least first and second electrical sections or housings as a single electronic assembly or module. The removable mechanical attachment system has first and second removable attachment members with each removable attachment member having first and second links. Each link has a base having front, back and sides with a bore extending through the base from the front to the back and a least a first extension member extending from one of the sides of the base. The links of the first removable attachment member are secured to respective first surfaces of the electrical sections or housings and links of the second removable attachment member are secured to respective second surface of the electrical sections or housings by securing members. The links of the first and second removable attachment members are disposed adjacent to open end faces of the electrical sections or housing. At least one of the extension members of the links of each of the first and second removable attachment members extends past one of the open end faces of the electrical sections or housings. The electrical sections or housings are positioned in a proximate abutting relationship at the open end faces with the extension members extending past the open end faces of the electrical sections or housings overlapping the other extension members of the first and second removable attachment members. A bonding material is applied to the overlapping extension members to join the extension members together.
The removable mechanical attachment system is preferably implemented with a plurality of extension member extending from the base of each of the links. At least one of the plurality of extension members of the first and second links of each of the first and second removable attachment members extends past one of the open end faces of the electrical sections or housing. Each of the links may also be implemented with a first extension member having tangs extending in a perpendicular direction from the extension member toward the front of the base. The second extension member of each of the first and second links of the first and second removable attachment members extend between the tines on the first extension member of each of the first and second links of the first and second removable attachment members. In the preferred embodiment, the extension members of the links extend past the open end faces of the electrical sections or housings.
Each link preferably has at least a first pedestal foot formed on the back of the base that engages a channel formed in each surfaces of the electrical sections or housings. In the preferred embodiment, each link has orthogonally disposed pedestal feet formed on the back of the base that engage orthogonally formed channels formed in each of the first and second surfaces of the first and second housings. Threaded apertures are formed at the intersection of the orthogonal channels with the threaded apertures receiving treaded screws that secure the links to the electrical sections or housings.
The extension members may be plated with a tin-lead alloy for receiving solder that is used as the bonding material. The bonding material may also include an adhesive, such a epoxy or the like. The bonding material may also be a strong adhesion low melting temperature metal, such as indium.